1. Field of the Invention
The present invention relates to a vehicle light for use as an automobile headlight or a supplementary headlight such as a fog light etc., and more particularly relates to a vehicle light which is designed for providing a low-beam mode light distribution pattern, capable of selectively providing a portion of light rays into a travelling direction of the vehicle such that a light amount in the travelling direction can be increased for providing a driver of the vehicle with improved visibility into the travelling direction of the vehicle. For example, when the vehicle drives on a curve to the left, a light amount to the left front of the vehicle can be increased. When the vehicle drives on a straight road at a relatively high speed, a light amount to a far front central area of the vehicle can be increased.
2. Description of the Related Art
Generally, a projection-type vehicle light comprises a light source, a major reflecting surface such as an ellipse group reflecting surface for reflecting light rays emitted from the light source in a direction generally forward, a projection lens of a convex lens whose convex surface is aspherical, etc., and a shade located in the vicinity of a focus of the projection lens. Light rays reflected by the major reflecting surface and directly come from the light source converge in the vicinity of the focus of the projection lens to provide a focused image of light. The projection lens projects the focused image of light upside down with its left side to be the right side into a forward direction while enlarging the focused image, thereby the projection-type vehicle light illuminates a predetermined area on a road. The shutter cuts off an unnecessary portion of light for formation of light distribution pattern(s) of the vehicle light. The unnecessary portion of light is typically a portion which generally illuminates in an upper right forward direction of the vehicle after being projected by the projection lens, which can be glare light to a driver of a car driving on an on-coming lane. Since light rays illuminating in the upper right forward direction of the vehicle are prohibited, an illuminated area of the vehicle light has a relatively short distance to the front of the vehicle at the side of the on-coming lane.
FIG. 25(A) illustrates a prohibited portion A of a low beam mode light distribution pattern on a screen defined by regulations and an actual light distribution pattern B on the screen for a vehicle driving on a left lane. The prohibited portion A is an area shown by slanting lines which light rays are not allowed to enter into in the low beam mode of the light distribution pattern. A horizontal line of the prohibited portion A located on the right side of the vertical axis is consistent with a horizontal axis on the screen. An inclined line of the prohibited portion A located on the left side of the vertical axis extends from a crossed point of a vertical axis and the horizontal axis on the screen to the left upward at 15 degrees relative to the horizontal axis. The actual light distribution pattern B is located not to enter into the prohibited portion A at any time of operation of the vehicle light.
When the vehicle drives on a curve, it is preferable for the vehicle light to provide an increased amount of light into a traveling direction, i.e., forward of the curve, of the vehicle in comparison with when driving on a straight road for obtaining superior long distance visibility on the curve. More specifically, when the vehicle drives on a curve to the left, it is preferable to increase an amount of light rays which illuminate a left side in front of the vehicle. On the other hand, when the vehicle drives on a curve to the right, it is preferable to increase an amount of light rays which illuminate a right side in front of the vehicle.
However, when the vehicle travels on a curve to the right, or turn around a corner to the right, even though the driver would like to see more clearly the forward of the curve or corner, there is a potential that sufficient bright field of vision is not obtained. The forward of the curve or corner is on the side of the on-coming lane. Since a cut-off line of the low beam mode light distribution pattern is fixed, the illuminated distance to the front right side from the vehicle cannot be increased.
Further, when the vehicle travels at a relatively high speed, a distance between the vehicle and another car traveling ahead increases. In this case, since light distribution characteristics of the vehicle light are fixed, an illuminated distance to the front of the vehicle results in being relatively decreased. It may happen that sufficient long distance visibility can not be obtained when the vehicle travels at a relatively high speed.
In order to achieve superior long distance visibility on the curve, in a conventional vehicle light, a reflecting surface laterally moves depending on steering angle while a location of a light source is fixed. The conventional projection-type vehicle light has the following problems.
In order to achieve sufficient change of a light distribution pattern between before and after the reflector is moved in accordance with the change of steering angle, a large space is required in a housing for moving an optical axis of the reflector at a large angle. Therefore, an entire size of the conventional vehicle light must be enlarged, and designing of the vehicle light tends to be difficult. Further, there exists gaps between a periphery of the reflector and aperture edge of the housing for allowing movement of the entire reflector, which deteriorates aesthetic appearance of the conventional vehicle light. Furthermore, a transparent front lens cannot be used, because it is difficult to obtain sufficient change of light distribution from when driving on a straight road to when driving on a curve solely by movement of the reflector. Prismatic cuts on an inner surface of the front lens are required to obtain the sufficient change of light distribution with superior visibility when a direction of an optical axis of the reflector is changed.
In another conventional vehicle light for the cases both when the vehicle drives on a curve or travels at a relatively high speed, an optical axis of the vehicle light is changed from a horizontal direction to an upward direction by moving an entire set of the vehicle light. In a still another conventional vehicle light, a shutter is moved to the downward. However, these two methods bring about increase of light amount illuminated to a still another vehicle running ahead of the vehicle. This problem is significant for a still another vehicle ahead of the vehicle running on a travelling lane when the vehicle travels on an over-passing lane. In general, a height of location of an automobile headlight disposed in an automobile body is lower than a position of a side mirror disposed in the automobile body. Therefore, if an illuminated light amount to the upward from the vehicle is increased, the upwardly illuminated light is reflected by the side mirror of another vehicle running ahead of the vehicle, which may cause to glare the driver in the vehicle running ahead of the vehicle on the traveling lane.
As a preventive means from the glare light, it is possible to detect a car running ahead of the vehicle, and to prevent from increasing light amount to the upward depending on detection results, e.g., a car running ahead of the vehicle is detected. However, a device for performing the detection and the illumination direction change must be large and expensive. Further, it is rarely that there is no car running ahead of the vehicle. Accordingly, this method is not very effective.
Then, the invention is, in part, intended to provide a vehicle light that includes a front lens substantially free from prismatic cuts, capable of easily changing an optical axis of a reflector, i.e., a general direction of a predetermined amount of light rays incident on the reflector, at a large angle by a simple structure while providing superior light distributions for both driving on a curve and driving on a straight road at a high speed. Specifically, when the vehicle drives on a curve or turn around a corner, the vehicle light is capable of increasing an illuminated distance to the front of the vehicle at the side of an on-coming lane without providing glare light to a driver of a car running on an on-coming lane.